It is often necessary or desirable to sense the presence, level or other characteristics of fluids. Thus, it is known to use sensors with storage tanks, reservoirs, fuel tanks and pipelines to determine fluid level, conditions of overfill or underfill, or to detect contamination. For example, sensors are used in gasoline storage tanks at service stations to monitor fluid level and to detect contamination in the outer water jacket now commonly installed around such fuel tanks.
Heretofore known sensors rely upon a variety of principles to measure the fluid level and other characteristics. The most common type of sensor is the capacitance type sensor. Unfortunately, these sensors require electrical power at the sensing location, creating a hazard of explosion when volatile fluids are being sensed. Optical sensors also have electrical components in the sensing zone and, thus, suffer from the same explosion hazard. In addition, prior optical sensors have been known to give false indications due to fluids adhering to optical surfaces.
Therefore, it is an object of the present invention to provide a fluid sensing device capable of performing various sensing functions without presenting any hazard of explosion.
Another object of the present invention is to provide a remote fluid sensor in which all electrical components are positioned away from the sensing zone.
Yet another object of the present invention is to provide a remote optical sensor which does not suffer from the undesirable effects of fluid films forming at the optical sensing tip.
Another object of the invention is to provide an optical fluid sensor in which the performance of the sensor components is monitored and a separate output signal provided to indicate failure of any components.
These and other highly desirable and unusual results are accomplished by the present invention in an economical structure in which all electrical components are disposed away from the sensing zone with only a non-electrical sensing tip in contact with the fluid in the sensing zone.
Objects and advantages of the invention are set forth in part herein and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the instrumentalities and combinations pointed out in the appended claims.
The invention consists in the novel parts, constructions, arrangements, combinations, steps, and improvements herein shown and described.